1. Field of the Invention
The present invention relates to a honeycomb structure and a method for manufacturing the honeycomb structure.
2. Discussion of the Background
Exhaust gases discharged from internal combustion engines such as diesel engines contain particulate matters (also termed PM hereafter) and possible adverse effects of the PM on environments and human bodies are a current issue.
Then, a variety of honeycomb filters using a honeycomb structure including silicon carbide and the like have been proposed as an exhaust gas filter for collecting the PM in exhaust gases and purifying the exhaust gases.
After collecting a certain amount of PM, the above-mentioned honeycomb structure undergoes a regenerating process in which the honeycomb structure is heated to a high temperature (about 600° C. to about 1000° C.) to burn the collected PM. Here, the PM tends to deposit unevenly in the longitudinal direction of the honeycomb structure forming the honeycomb filter. This causes temperature differences along the longitudinal direction of the honeycomb structure as the PM burns. Consequently, the honeycomb structure undergoes thermal stress. Particularly, in the honeycomb structure obtained by bonding a plurality of honeycomb fired bodies using an adhesive layer, the thermal stress may impose a load on the adhesive layer and cause cracks of the adhesive layer.
When the cracks develop extensively through the adhesive layer as a result of further regenerating processes or vibrations during the driving, the adhesive strength between honeycomb fired bodies is lowered, whereby some honeycomb fired bodies may be displaced or even some honeycomb fired bodies may come off in an extreme case. The displacement or coming off of the honeycomb fired body may cause exhaust gas leakage.
In order to prevent any displacement or coming off of the honeycomb fired bodies, a honeycomb structure of which the honeycomb fired bodies have fine recessed and projected portions on their peripheral face to improve the adhesive strength to the adhesive layer has been proposed (JP-A 2000-279729).
The contents of JP-A 2000-279729 are incorporated herein by reference in their entirety.